EDM with jump motion detecting reactive force

ABSTRACT

An electric discharge machine for machining a workpiece by an electric discharge by supplying a machining fluid to a gap between an electrode and the workpiece and supplying pulses to the workpiece while providing the electrode with a jump motion having a periodic motion of the electrode relative to the workpiece; wherein the electric discharge machine detects a state quantity caused in a main body of the electric discharge machine by a reactive force produced by a machining operation in the gap between the electrode and the workpiece and changes machining conditions of the workpiece in accordance with a detected value of the state quantity.

This is a divisional of Application Ser. No. 08/568,682 filed Dec. 7,1995 now U.S. Pat. No. 5,973,498, the disclosure of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an electric discharge machine,particularly to an electric discharge machine which, in case where themain body of the electric discharge machine is deformed by a reactiveforce caused by the electric discharge machining, controls the reactiveforce or a deformation of the main body of the electric dischargemachine within a certain value or at a constant amount.

DISCUSSION OF BACKGROUND

FIG. 6 is a structural view of a general type of a conventional electricdischarge machine.

In FIG. 6, numeral 1 designates an electrode, numeral 2 designates aworkpiece, numeral 3 designates a machining fluid, numeral 4 designatesa machining tank, numeral 5 designates an electrode rotating devicerotating the electrode 1 around-a Z axis, numeral 6 designates a Y-axistable, numeral 7 designates a Y-axis driving device driving the Y-axistable, numeral 8 designates a X-axis table, numeral 9 designates aX-axis driving device driving the X-axis table, numeral 10 designates aZ-axis driving device driving the electrode rotating device 5 attachedwith the electrode 1 in Z-axis direction, numeral 11 designates anelectric source supplying pulses between the electrode 1 and theworkpiece 2, numeral 12 designates a machining state detecting devicedetecting a machining state in machining, numeral 13 designates amachining fluid supplying device supplying the machining fluid to thegap of machining and numeral 14 designates a NC control device. FIG. 7is a block diagram for explaining the operation of the electricdischarge machine shown in FIG. 6. In FIG. 7, parts 11, 12, 13 and 14are the same as those in FIG. 6. Numeral 15 designates a machiningcondition setter setting various machining conditions to the electricsource 11, the machining fluid supplying device 13, a machining pathdesignator 16, a jump motion controller 17 and a comparator 18. Thenumeral 16 designates the machining path designator generating a pathfor machining the workpiece in a desired shape, an electrode planetarypattern and the like, the numeral 17 designates the jump motioncontroller for having the electrode 1 rise and fall during the machiningoperation, the numeral 18 is the comparator, a numeral 19 designates amachining controller and numeral 20 designates a machining/jump motionswitcher. The operation of these parts 15 through 20 is generallyrealized by a program in the NC control device 14. Numeral 21 designatesan electrode driving device which is constituted by the electroderotating device 5, the respective axis tables and the respective axisdriving devices 6 through 10. Numeral 22 designates a dischargemachining process indicating a discharge machining phenomenon causedbetween the electrode 1 and the workpiece 2 opposedly arranged in themachining fluid 3.

Next, an explanation will be given of the operation.

In a normal electric discharge machine a gap distance control system isconstituted for adjusting a gap between the electrode 1 and theworkpiece 2 for machining the workpiece in a desired shape whilemaintaining a stable machining state. The control system compares areference instruction value set by the machining condition setter 15with a detected value indicating the electric discharge machiningprocess 22 that is detected by the machining state detecting device 12,by the comparator 18, calculates a deviation and issues an electrodemovement instruction based on an instruction from the machining pathdesignator 16 such that the deviation is nullified by the machiningcontroller to thereby control the gap between the electrode 1 and theworkpiece 2. Further, the machining is finished at a time point wherethe electrode movement instruction value becomes a final instructionvalue of the desired shape. In this case machining is selected in themachining/jump motion switcher 20.

The NC control device 24 has a function of the jump motion control aswell as a function of the gap distance control. In the jump motion themachining/jump motion switcher 20 forcibly switches the gap distancecontrol to the jump motion whereby the electrode 1 is risen and fallen.This jump motion is important in view of stabilizing the machining stateby evacuating debris from the gap of machining by its pumping operation.

However, in such an electric discharge machine a large positive pressureor negative pressure (hereinafter reactive force by working or workingreaction) is operated on the electrode in rising or falling of theelectrode in the jump motion, in case where the electrode is especiallylarge or the gap of machining is very narrow as in a finishing operationor the depth of machining is large whereby the main body of the electricdischarge machine is deformed and the machining accuracy isdeteriorated. According to a research by Mohri et al at Toyoda Instituteof Technology "Study on The Characteristics of Electrical DischargeMachining (EDM) in Real Operation", Journal of the Japan Society ofElectrical-Machining Engineers, vol. 20, No. 39, p.19-29, 1987, theabove-mentioned force operating on the electrode is caused by theviscosity of a machining fluid and a force operating on the electrodewhen the electrode is falling, especially causes the deterioration ofthe machining accuracy.

FIGS. 8A, 8B and 8C illustrate a main shaft displacement, a workingreaction and a column displacement in a jump motion actually measured byMohri et al. As is apparent from a portion A in the figures the workingreaction is maximized when the electrode is falling. Incidentally, inthese figures the main shaft designates the Z axis and the columnindicates the main body of the machine supporting the Z axis,respectively and the working reaction is measured by a force sensorintegrated in an electrode attaching jig.

To solve the above-mentioned problem Mohri et al proposed that therigidity of the machine is to be enhanced by a planer-type structure andthe working reaction is to be alleviated by reducing an electrodefalling speed immediately before the falling of the electrode isfinished to thereby decrease the deformation of the column.

A portion B in FIG. 8 shows that the working reaction is smaller thanthat in the portion A and hence the amount of displacement of the columnis reduced. This is due to the decelerated falling speed of the mainshaft in the portion B that is a result supporting the proposal of Mohriet al.

Japanese Examined Patent Publication No. 31806/1992 discloses a methodof controlling an electrode speed in the jump motion based on the sameconception. As shown in FIG. 9 in this method the speed is changed inrising and falling of the electrode in accordance with a distancebetween the electrode and the workpiece. In FIG. 9, in rising of theelectrode the electrode rising speed is accelerated from v2 to v1 at adistance L1 between the electrode and the workpiece and in falling ofthe electrode the electrode falling speed is decelerated from v1 to v2at the distance L1 between the electrode and the workpiece by which thepositive pressure and the negative pressure operating on the electrodeare alleviated.

Incidentally, in the paper of Mohri et al the area of the electrode isdescribed only up to approximately 20 cm². FIGS. 10A and 10B indicatethe main shaft displacement and the column displacement in a finishingoperation while performing a jump operation in which an electrode havingthe area of the electrode of approximately 1000 cm² is used. In the jumpoperation the electrode falling speed is controlled to decelerateimmediately before the electrode falling is finished. Therefore,although a column displacement is caused in rising of the electrode,almost no column displacement is caused in falling the electrode.However, a noteworthy point in FIG. 10 in comparison with FIG. 8 is thata large column displacement is caused at portions C during time periodsin which electric discharge is generated between the electrode and aworkpiece (hereinafter, in discharging). There has been no descriptionwith regard to the phenomenon in which the column displacement is causedin discharging.

The column displacement shown here is caused not only by a force due tothe viscosity of a machining fluid which has conventionally beenrecognized but by a pressure of a great number of bubbles generated atthat occasion by vaporizing the machining fluid confined in the gap ofmachining by a continuous electric discharge. Therefore, the columndeformation is not limited to that in the jump operation. Whatinfluences on the actual machining accuracy is predicted to be ratherthe column displacement in discharging mentioned here than theabove-mentioned column displacement in rising and falling of theelectrode.

As stated above the conventional electric discharge machine cannot dealwith the force received by the electrode by accumulating the bubbles ofthe machining fluid generated in discharging at the gap between theelectrode and the workpiece. Accordingly, the main body of the electricdischarge machine is deformed by the pressure of the bubbles causing awork shape error due to the deformation of X, Y and Z axes to beorthogonal to each other and a working dimension error due to the changeof the reference position per se and accordingly a sufficient machiningaccuracy cannot be realized. Further, the machining is finished at atime point when the electrode movement instruction value becomes thefinal instruction value of the desired shape without considering thedeformation of the main body of the machine and accordingly, the workshape error is caused. Moreover, the force acting on the electrodeoperates as a disturbance to the gap distance control system and astable machining state cannot be maintained when the pressure is rapidlychanged in case where the bubbles are detached from the gap of machiningor the bubbles are liquefied again, giving rise to the lowering of themachining speed.

SUMMARY OF THE INVENTION

It is an object of the present invention to resolve the above-mentionedproblem and to realize an electric discharge machine capable ofimproving lowering of machining accuracy and machining speed caused by areactive force by working generated especially in discharging.

According to a first aspect of the present invention, there is providedan electric discharge machine for machining a workpiece by an electricdischarge by supplying a machining fluid to a gap between an electrodeand the workpiece and supplying pulses to the workpiece while providingthe electrode with a jump motion, said jump motion being a periodicmotion of the electrode relative to the workpiece;

wherein said electric discharge machine detects a state quantity causedin a main body of the electric discharge machine by a reactive forceproduced by a machining operation in the gap between the electrode andthe workpiece and changes machining conditions of the workpiece inaccordance with a detected value of the state quantity.

According to a second aspect of the present invention, there is providedthe electric discharge machine according to the first aspect, whereinthe state quantity is an amount of a force caused in the main body ofthe electric discharge machine corresponding to the reactive force.

According to a third aspect of the present invention, there is providedthe electric discharge machine according to the first aspect, whereinthe state quantity is an amount of a deformation caused in the main bodyof the electric discharge machine corresponding to the reactive force.

According to a fourth aspect of the present invention, there is providedthe discharge machining device according to the first aspect, whereinthe machining conditions to be changed include at least one selectedfrom the group consisting of an onset timing of the jump motion, acontinuous time period of the pulses, on and/or off time periods of eachof the pulses, a current value and/or a gap voltage of the pulses, aswitching of sucking and exhausting the machining fluid, an amount ofsucking and/or exhausting the machining fluid and a pressure of suckingand/or exhausting the machining fluid.

According to a fifth aspect of the present invention, there is providedan electric discharge machine for machining a workpiece by an electricdischarge by supplying a machining fluid to a gap between an electrodeand the workpiece and supplying pulses to the workpiece while providingthe electrode with a jump motion, said jump motion being a periodicmotion of the electrode relative to the workpiece;

wherein said electric discharge machine detects a reactive forceproduced by a machining operation in the gap between the electrode andthe workpiece or an amount of a deformation caused in a main body of theelectric discharge machine by the reactive force and performs a secondjump motion restraining the reactive force in accordance with thereactive force or the amount of the deformation.

According to a sixth aspect of the present invention, there is providedan electric discharge machine for machining a workpiece by an electricdischarge by supplying a machining fluid to a gap between an electrodeand the workpiece and supplying pulses to the workpiece while providingthe electrode with a jump motion, said jump motion being a periodicmotion of the electrode relative to the workpiece;

wherein said electric discharge machine detects a reactive forceproduced by a machining operation in the gap between the electrode andthe workpiece or an amount of a deformation caused in a main body of theelectric discharge machine by the reactive force and determines that themachining operation on the workpiece has been finished when the detectedvalue is equal to or less than a predetermined value.

According to a seventh aspect of the present invention, there isprovided an electric discharge machine for machining a workpiece by anelectric discharge by supplying a machining fluid to a gap between anelectrode and the workpiece and supplying pulses to the workpiece whileproviding the electrode with a jump motion, said jump motion being aperiodic motion of the electrode relative to the workpiece;

wherein said electric discharge machine detects a reactive forceproduced by a machining operation in the gap between the electrode andthe workpiece or an amount of a deformation caused in a main body of theelectric discharge machine by the reactive force and corrects a path ofthe machining operation determining a position of the electrode relativeto the workpiece.

According to the first aspect of the electric discharge machine thestate quantity caused in the main body of the electric discharge machineby the reactive force produced by the machining operation in the gapbetween the electrode and the workpiece is detected and the machiningconditions of the workpiece are changed in accordance with the detectedvalue by which a stable working is provided and the machining speed andthe machining accuracy are improved.

According to the second aspect of the electric discharge machine theamount of the force caused in the main body of the electric dischargemachine corresponding to the reactive force is detected as the statequantity in the first aspect by which a stable machining state isprovided and the machining speed and the machining accuracy areimproved.

According to the third aspect of the electric discharge machine theamount of the deformation caused in the main body of the electricdischarge machine is detected as the state quantity in the first aspectby which a stable machining state is provided and the machining speedand the machining accuracy are improved.

According to the fourth aspect of the electric discharge machine atleast one selected from the group consisting of an onset timing of thejump motion, a continuous time period of the pulses, on and/or off timeperiods of each of the pulses, a current value and/or a gap voltage ofthe pulses, a switching of sucking and exhausting the machining fluid,an amount of sucking and/or exhausting the machining fluid and apressure of sucking and/or exhausting the machining fluid, is changed bywhich a stable machining state is provided and the machining speed andthe machining accuracy are improved.

According to the fifth aspect of the electric discharge machine thereactive force produced by the machining operation in the gap betweenthe electrode and the workpiece or the amount of the deformation causedin the main body of the electric discharge machine by the reactiveforce, is detected and the second jump motion restraining the reactiveforce in accordance with the reactive force or the amount of thedeformation, is performed by which a stable machining state is providedand the machining speed and the machining accuracy are improved.

According to the sixth aspect of the electric discharge machine thereactive force produced by the machining operation in the gap betweenthe electrode and the workpiece or the amount of the deformation causedin the main body of the electric discharge machine by the reactiveforce, is detected and the machining operation on the workpiece isdetermined to be finished when the detected value is equal to or lessthan the predetermined value by which a stable machining state isprovided and the machining speed the machining accuracy are improved.

According to the seventh aspect of the electric discharge machine thereactive force produced by the machining operation in the gap betweenthe electrode and the workpiece or the amount of the deformation causedin the main body of the electric discharge machine by the reactiveforce, is detected and the path of the machining operation determiningthe position of the electrode relative to the workpiece, is corrected bywhich a stable machining state is provided and the machining speed andthe machining accuracy are improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the operation of an electric dischargemachine in a first embodiment of the present invention;

FIG. 2 is a block diagram showing the operation of an electric dischargemachine in a second embodiment of the present invention;

FIGS. 3A and 3B illustrate diagrams explaining a jump motion in thesecond embodiment of the present invention;

FIG. 4 is a block diagram showing the operation of an electric dischargemachine in a third embodiment of the present invention;

FIG. 5 is a block diagram showing the operation of an electric dischargemachine in a fourth embodiment of the present invention;

FIG. 6 is a diagram showing the structure of a conventional electricdischarge machine;

FIG. 7 is a block diagram showing the operation of a conventionalelectric discharge machine;

FIGS. 8A, 8B and 8C illustrate diagrams measuring a reactive force by amachining operation caused by the viscosity of a machining fluid in jumpmotion;

FIG. 9 is a diagram showing a jump motion in a conventional electricdischarge machine; and

FIGS. 10A and 10B illustrate diagrams measuring a reactive force by amachining operation bubbles generated by vaporizing a machining fluid indischarging.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

EMBODIMENT 1

An explanation will be given of a first embodiment of the presentinvention as follows. FIG. 1 is a block diagram explaining the operationof a first embodiment of an electric discharge machine. In FIG. 1 parts11 through 13 and 16 through 22 are the same as those in theconventional example shown by FIG. 7. Numeral 23 designates a workingreaction detecting device detecting a working reaction or a reactiveforce caused by a machining operation in discharging, numeral 24designates a machining condition changing device and numeral 25designates a variable machining condition setter different from theconventional machining condition setter and having a function capable ofchanging machining condition set values by an instruction from themachining condition changing device 24.

In this embodiment a working reaction in discharging is detected by theworking reaction detecting device 23 and the machining conditionchanging device 24 instructs the change of the machining conditions tothe variable machining condition setter 25 such that the detected valueis not equal to or more than a predetermined value or stays constant. Asthe working reaction detecting device 23, for example, a motor currentof the electrode driving device, a torque sensor attached to theelectrode driving device, a force sensor attached to a jig for theelectrode or the main body of the electric discharge machine or the likecan be used. Further, as the machining conditions to be changed, one orcombinations selected from the group consisting of an onset timing ofthe jump motion, a continuous time period of the pulses, on and/or offtime periods of each of the pulses, a current value and/or a gap voltageof the pulses, a switching of sucking and exhausting the machiningfluid, an amount of sucking and/or exhausting the machining fluid and apressure of sucking and/or exhausting the machining fluid, can be used.As mentioned above the main cause of the working reaction is thatbubbles generated by vaporizing the machining fluid by the electricdischarge are confined in a narrow gap of machining. Therefore, when theabove-mentioned machining conditions are changed, the bubbles in the gapof machining are restrained from generating, or the operation of lettingthe generated bubbles escape from the space of working is accelerated.As a result it is possible to promote the machining accuracy byrestraining the deformation of the main body of the electric dischargemachine caused by the working reaction.

Further, although in this embodiment the working reaction in dischargingis detected by the working reaction detecting device 23, an amount ofdeformation of the main body of the electric discharge machine indischarging may be detected. In this case, as means of detecting theamount of deformation, for example, an optical length measuringequipment, an eddy current type length measuring equipment, adifferential transformer type length measuring equipment, an ultrasonictype length measuring equipment, a strain gage and the like, can beused.

Although the explanation has been given of the first embodiment of theelectric discharge machine, the working reaction detecting device 23,the machining condition changing device 24 and the variable machiningcondition setter 25 shown in FIG. 1 may respectively be constructed asexclusive devices or may be realized in the NC control device 14 asprograms.

EMBODIMENT 2

An explanation will be given of a second embodiment of the presentinvention as follows. FIG. 2 is a block diagram explaining the operationof a second embodiment of an electric discharge machine. In FIG. 2 parts11 through 13, 16 and 18 through 25 are the same as shown inEmbobodiment 1. Numeral 26 designates a composite-jump motioncontroller.

In this embodiment the working reaction in discharging is detected bythe working reaction detecting device 23 and the composite-jump motioncontroller 26 controls a second jump motion such that the detected valuebecomes equal to or less than a predetermined value. FIGS. 3A and 3Bindicate the jump motion by the conventional jump motion controller andthe jump motion by the composite-jump motion controller of thisembodiment. In FIGS. 3A and 3B notation D designates first jump motionscorresponding to the conventional jump motions. Further, notation Edesignates second jump motions which are pertinently performed in theintervals of the first jump motions. In the jump motion of thisembodiment, in addition to the first jump motion for evacuating debrisfrom the gap of working as in the conventional example, the workingreaction is controlled based on the detected value which has beendetected by the working reaction detecting device 23 and the onset ofthe jump motion and a jump rise distance are adaptively controlled inthe second jump motion. Accordingly, the evacuation of debris from thegap of machining and at the same time the control of the workingreaction can effectively be realized and the deformation of the mainbody of the electric discharging machine by the working reaction can berestrained while stably maintaining the machining state by which themachining speed and the machining accuracy can be promoted.

Further, the structure of the working reaction detecting device 23 inthis embodiment and the machining conditions to be changed may be thesame as those in Embodiment 1.

Further, the machining condition changing device 24 is not necessary incase where only the second jump motion is controlled and it is apparentin this case that the variable machining condition setter 25 is the sameas the conventional machining condition setter.

Although in this embodiment the working reaction in discharging isdetected by the working reaction detecting device 23, as explained inEmbobodiment 1, the amount of deformation of the main body of theelectric discharge machine in discharging may be detected. The means fordetecting the amount of deformation may be the same as those inEmbodiment 1. It is naturally possible to combine the embodiment withthe function of Embobodiment 1.

Although the explanation has been given of the second embodiment of theelectric discharge machine, the composite-jump motion controller 26 inthis embodiment may be constructed as an exclusive device or may berealized as a program in the NC control device 14.

EMBODIMENT 3

An explanation will be given of a third embodiment of the presentinvention. FIG. 4 is a block diagram explaining the operation of thethird embodiment of an electric discharge machine. In FIG. 4 notation 15designates the conventional part as shown in FIG. 7 and parts 11 through13, 16 through 18 and 20 through 23 are the same as those shown inEmbobodiment 1. Numeral 27 designates a machining depth evaluationcontroller and numeral 28 designates a machining controller withmachining finish evaluation function different from the conventionalmachining controller and evaluating finishing of the machining operationbased on an instruction from the machining depth evaluation controller27.

In this embodiment the working reaction in discharging is detected bythe working reaction detecting device 23 and the machining depthevaluating controller 27 issues an instruction evaluating the depth ofmachining to the machining controller with machining finish evaluatingfunction 28 and evaluates the machining depth when the detected value isequal to or less than a certain value. That is, the finishing of themachining operation is determined when the amount of deformation of themain body of the electric discharge machine by the working reaction isequal to or less than an allowable value and accordingly the desiredmachining depth can accurately be machined.

Although the working reaction in discharging is detected by the workingreaction detecting device 23 in this embodiment, as explained inEmbobodiment 1, the amount of deformation of the main body of theelectric discharging machine in discharging may be detected and themachining depth may be evaluated based on the amount of deformation.Further, a deformation amount calculating device for calculating theamount of deformation from the working reaction may be provided. It isnaturally possible to combine this embodiment with the functions ofEmbobodiment 1 and/or Embodiment 2.

Although the explanation has been given to the third embodiment of theelectric discharging machine, the machining depth evaluation controller27 and the machining controller with machining finish evaluatingfunction 28 may be constructed respectively as exclusive devices and maybe realized in the NC control device 14 as programs.

EMBODIMENT 4

An explanation will be given of a fourth embodiment of the presentinvention as follows. FIG. 5 is a block diagram explaining the operationof an electric discharge machine in the fourth embodiment. In FIG. 5 thepart 15 is the same as the conventional one shown in FIG. 7 and theparts 11 through 13 and 17 through 23 are the same as those shown inEmbobodiment 1. Further, numeral 29 designates a deformation calculatorcalculating a deformation of the main body of the electric dischargemachine by the working reaction detected by the working reactiondetecting device 23 and numeral 30 designates a working path compensatorwith path correcting function which corrects a working path instructionbased on an amount of deformation calculated by the deformationcalculator 29.

In this embodiment the working reaction detecting device 23 detects theworking reaction in discharging, the deformation calculator 29calculates the amount of deformation of the main body of the electricdischarge machine from the detected value and the working pathcompensator with path correcting function 30 issues the working pathinstruction after performing a correction based on the amount ofdeformation. Therefore, a highly accurate machining correcting theamount of deformation of the main body of the electric discharge machinecan be realized.

In this embodiment, the working reaction in discharging is detected bythe working reaction detecting device 23 and the amount of deformationof the main body of the electric discharging machine is calculated fromthe detected value by the deformation calculator 29. However, as hasbeen explained in Embobodiment 1, the amount of deformation of the mainbody of the electric discharge machine in discharging may directly bedetected and the working path may be corrected based on the amount ofdeformation. It is naturally possible to combine the embodiment with thefunctions of either one or arbitrary two of the Embobodiment 1 throughEmbodiment 3.

Although the explanation has been given of the electric dischargingmachine in the fourth embodiment, the working path compensator with pathcorrecting function 30 shown in FIG. 5 may be constructed as anexclusive machine or may be realized in the NC control device 14 as aprogram.

According to the first aspect of the present invention the statequantity caused in the main body of the electric discharge machine bythe reacting force produced by the machining operation in the gapbetween the electrode and the work piece, namely, the working reactionis detected and the machining conditions of the work piece are changedby the detected value by which the deformation of the main body of theelectric discharge machine by the working reaction can be restrained.Therefore, both the machining speed and the machining accuracy arepromoted while a stable machining state can be maintained.

According to the second aspect of the present invention the statequantity caused in the main body of the electric discharge machine bythe working reaction between the electrode and the workpiece is detectedas the force amount by a motor current of the electrode driving device,a torque sensor attached to the electrode driving device, a force sensorattached to a main body of the electrode, a jig for the electrode or themain body of the electric discharge machine, or the like and thedeformation of the main body of the electric discharge machine by theworking reaction can be restrained by changing the machining conditionsof the workpiece by the detected value. Therefore, both the machiningspeed and the machining accuracy are promoted while a stable machiningstate can be maintained.

According to the third aspect of the present invention the statequantity caused in the main body of the electric discharging machine bythe working reaction between the electrode and the workpiece is detectedas the amount of deformation by an optical type length measuringequipment, an eddy current type length measuring equipment, adifferential transformer type length measuring equipment, an ultrasonictype length measuring equipment, a strain gage, etc. and the deformationof the main body of the electric discharge machine by the workingreaction is restrained by changing the machining conditions of theworkpiece by the detected value. Therefore, both the machining speed andthe machining accuracy can be promoted while a stable machining statecan be maintained.

According to the fourth aspect of the present invention the statequantity caused in the main body of the electric discharge machine bythe working reaction between the electrode and the workpiece is detectedby the amount of force or the amount of deformation and the deformationof the main body of the electric discharge machine by the workingreaction is restrained by changing the machining conditions such as anonset timing of the jump motion, a continuous discharge time period ofthe pulses, an on time or an off time of each of the pulses, a currentvalue or a gap voltage of the pulses, a switching of sucking andexhausting a machining fluid, an amount of sucking or exhausting themachining fluid, a pressure of sucking or exhausting the machining fluidor the like. Therefore, both the machining speed and the machiningaccuracy are promoted while a stable machining state can be maintained.

According to the fifth aspect of the present invention, the statequantity caused in the main body of the electric discharge machine isdetected by the working reaction in the gap between the electrode andthe workpiece and the deformation of the main body of the electricdischarge machine by the working reaction can be restrained byperforming the second jump motion restraining the working reaction inaccordance with the state quantity. Therefore, both the machining speedand the machining accuracy are promoted while a stable machining statecan be maintained.

According to the sixth aspect of the present invention, the statequantity caused in the main body of the electric discharge machine bythe working reaction between the electrode and the workpiece is detectedand it is determined that the machining operation of the workpiece hasbeen finished when the detected value is equal to or less than apredetermined value. Therefore, both the machining speed and themachining accuracy are promoted while a stable machining state can bemaintained.

According to the seventh aspect of the present invention, the statequantity caused in the main body of the electric discharge machine bythe working reaction between the electrode and the workpiece is detectedand the machining path determining a position of the electrode relativeto the workpiece is corrected. Therefore, both the machining speed andthe machining accuracy are promoted while a stable machining state canbe maintained.

What is claimed is:
 1. An electric discharge machine for machining aworkpiece, disposed within a machining tank of the electric dischargemachine, using an electric discharge by supplying a machining fluid to agap between an electrode and the workpiece and supplying pulses to theworkpiece while providing the electrode with a jump motion, said jumpmotion being a periodic motion of the electrode relative to theworkpiece, said electric discharge machine comprising:a detector whichdetects a change in a state quantity of a main body of the electricdischarge machine, the change in the state quantity caused by a reactiveforce produced by a machining operation in the gap between the electrodeand the workpiece; and circuitry which changes machining conditionsassociated with the workpiece in accordance with a detected value of thestate quantity to reduce the change in the state qualitity.
 2. Theelectric discharge machine as recited in claim 1, wherein the statequantity is an amount of a force applied to the main body of theelectric discharge machine corresponding to the reactive force.
 3. Theelectric discharge machine as recited in claim 1, wherein the statequantity is an amount of deformation caused in the main body of theelectric discharge machine corresponding to the reactive force.
 4. Thedischarge machining device as recited in claim 1, wherein the machiningconditions to be changed include at least one machining conditionselected from the group consisting of:an onset timing of the jumpmotion; a continuous time period of the pulses; on and/or off timeperiods of each of the pulses; a current value and/or a gap voltage ofthe pulses; a switching of suctioning and exhausting the machiningfluid; an amount of the suctioning and/or the exhausting of themachining fluid; and pressure used in the suctioning and/or theexhausting operations with respect to the machining fluid.
 5. Thedischarge machining device as recited in claim 1, wherein said circuitrycomprises:first means, operatively connected to said detector, fordesignating a change to said machining conditions; second means,electrically coupled to said first means for establishing initialmachining conditions prior to machining and for changing said initialmachining conditions to adjusted machining conditions responsive to thedesignated change identified by said first means.
 6. The dischargemachining device as recited in claim 1, wherein said circuitrycomprises:a machining condition changing circuit, operatively connectedto said detector, which designates a change to said machiningconditions; variable machining condition controller, electricallycoupled to said machining condition changing circuit which appliesinitial machining conditions prior to commencement of the machiningoperation and which exchanges said initial machining conditions foradjusted machining conditions responsive to the designated changeidentified by said machining condition changing circuit.
 7. Thedischarge machining device as recited in claim 1, wherein said detectorcomprises a detection means for detecting a change in lengthattributable to said reactive force.